1. Introduction
Ensuring horse welfare is vital for riders and owners alike, both for ethical reasons and to ensure their health and happiness. From an ethical perspective, it may be argued that because we use horses for sport and leisure, we have a responsibility to protect their wellbeing, not only in preventing suffering, but also in promoting positive emotional states, as Mellor & Burns [
1] concluded. The theoretical framework of animal welfare has been revised in 2015 by Mellor & Beausoleil [
2] to include five domains (nutrition, environment, health, behavior, and mental state) and emphasize the importance of positive mental states. Furthermore, Mellor & Burns [
1] have developed a practical assessment model for equine welfare, within which the present study is particularly concerned with the domains of Environment and Behavior. Housing horses in an open barn system may substantially benefit their welfare, as it gives them more choice, allows access to a larger space, and provides the opportunity to move around at all times. Yngvesson et al. [
3] found that horses in Swedish riding schools were in better general health when kept in group housing then when they were housed individually and they had a lower incidence of respiratory problems and colic. Additionally, the open barn system is conducive to an improved working environment, as difficult and time-consuming tasks can be mechanized. The basic design consists of a lying hall, where the horses are provided with a dry and comfortable lying surface, and a paddock around the lying hall, with forage delivered ad lib or by computer-aided feeding stations. However, open barns can differ greatly in their planning and management. More research data are thus required to develop guidelines for suitable layouts, ensuring the sustainability of the horses’ welfare.
An important factor in the welfare of horses is the opportunity to get enough sleep. Horses move through four stages of vigilance: wakefulness, drowsiness, slow wave sleep, and paradoxical sleep [
4,
5,
6]. Even though horses can sleep while standing, they also need to lie down and rest their heads, which happens during paradoxical sleep. Monitoring the horses’ lying time can be used to compare different housing systems from a welfare perspective [
7]. It has been observed that feral horses tend to spend 0.5–2 h lying down during a 24 h period [
8,
9,
10,
11], and foals and young horses (2–3 years old) tend to spend even longer [
9]. Individually stalled horses usually spend 3–5 h lying down during a 24 h period [
4,
5,
12], while lying time for horses kept in open barns reportedly ranges from 1 to 2 h [
13,
14]. Raspa et al. [
15] suggested that the longer lying times found in stalled young horses compared to feral young horses could be due to boredom and restricted space. Using an automatic concentrate station increased lying time from 84 ± 42 min to 115 ± 71 min per day [
14]. In the same study, they found that the lying periods in this active open barn seemed to occur between the hay feeding times.
Total lying time can vary according to several factors. It tends to be shorter, for example, in hot climates [
16], and longer with increased exercise [
17]. Köster et al. [
12] found that horses kept in open barns had shorter lying times than those kept in individual boxes, and horses kept in open barns were said to have similar lying times [
13,
14,
18] to feral horses [
8,
10,
11]. Studies also show that as many as one-third of horses kept in active open barns do not lie down every day [
19]. Lower-ranked horses in open barns spend little to no time lying down when compared with higher-ranked horses [
19,
20,
21], especially when the lying area is restricted [
21]. Lower-ranked horses reportedly exhibit fewer lying bouts than higher-ranked horses [
19] because their lying bouts are often disturbed or interrupted [
20]. In comparing the activity levels of stabled horses and horses kept in open barns, Gansow [
22] found a negative correlation between activity level and rank for the horses kept in open barns.
Fader & Sambraus [
21] found that the size of the lying area influenced time spent lying down. Horses in open barns with a smaller lying area (4.6 m
2/horse, 59 ± 48 min) spent significantly less time lying down (
p < 0.01) than horses with access to a larger lying area (10.0 m
2/horse, 103 ± 73 min, 17.3 m
2 per horse, 134 ± 37 min). In two of the open barns, the lying area was divided between two lying halls, and the lying time for those herds did not differ significantly from the other herds. Moreover, Raabymagle & Ladewig [
23] found that lying time was shorter in smaller boxes ((1.5 times withers’ height of the horse)
2 m
2) compared with larger boxes ((2.5 times withers’ height of the horse)
2 m
2). In an open barn housed by broodmares, the proportion of the herd using the lying hall increased when the number of horses was reduced, which basically increased the available lying area from 7 to 17 m
2 [
24]. The same study found that the mares used the lying hall in turns at a higher occupancy rate, suggesting that they divided themselves into subgroups. Swedish legislation for animal welfare stipulates that the minimum lying area in open barns must be 8 m
2/horse for large horses (determined by height of the withers over 1.71 m) when they are being fed outside the lying hall, and 10 m
2/horse when they are being fed inside [
25]. Besides lying area, bedding material seems to be another factor that influences lying time, both in boxes and open barns. Extending the area covered by soft bedding materials, such as straw or wood shavings, increased both lying time and duration [
20]. Lying times in an active open barn were found to be longest for shavings (74.3 ± 2.87 min), followed by rubber mats (62.3 ± 2.27 min), and then sand (43.0 ± 2.33 min) [
19]. Using rubber mats instead of wood shavings in single boxes led to shorter lying times [
26]. Werhahn et al. [
27] found that foraging increased when straw bedding was used, indicating that this kind of bedding poses the risk of interrupting lying bouts.
Furthermore, horses’ use of lying halls seems to be determined by the weather, and wet and windy conditions have been shown to increase the use of lying halls [
28,
29,
30]. Feral horses also exhibit this behavior, seeking both shade and shelter from insect harassment [
31], as well as protection from the wind and rain [
32]. Individual spacing area is another factor that could influence the use of lying halls. Keiper & Sambraus [
33] found that stallions spend most of their time with 1 m to 10 m between themselves and other horses. Mares tended to require less individual space, because they were broodmares with offspring nearby. Differences in individual spacing area, where foals were found to be more willing to share space than older horses [
30], indicate that the adult horse’s individual space requirements are likely to be >1 m.
On this basis, we believe there is demand for research into the “best practice” for planning and managing animal welfare in open barns, which should not be dictated solely by minimum requirements. Sleep is an important factor in the welfare of horses and lying time for stalled horses seems to vary according to such factors as climate, exercise, bedding, housing, and lying area. To ensure the wellbeing of the horses in this type of housing system, it is critical that lying areas provide the opportunity for adequate rest and sleep.
The aim of this study was to analyze time spent in, as well as activity taking place in, lying halls of varying sizes. The study had three research questions: How does the use of lying halls depend on available lying area? In what way does the lying time differ in individual boxes compared to shared lying area in an open barn? How do variations in total available lying area affect lying time? The hypothesis was that increasing available lying area would increase total lying time.
4. Discussion
Housing horses in an open barn system may substantially improve their welfare, as Yngvesson et al. [
3] found, provided that the horse’s nutritional needs are also met and that they are part of a suitable social group where competition for lying space is low. Ensuring their welfare does not only mean preventing suffering, but also promoting positive emotional states [
1]. The domains Environment & Behavior are particularly relevant in open barns when the horse has more choices [
2]. The aim of this study was to analyze time spent, as well as activity taking place in, lying halls of various sizes. To answer the questions following the aim, we used two different studies. In the first study we received an answer for the use of and lying time in a lying hall. To follow up these findings we continued with the second study to analyze if the use of lying halls and lying time depended on available area. In the second study we also compared lying time in solitary and shared spaces. The lying area of 8 m
2/horse in Study 2 was chosen based on the minimum requirement for a horse of a particular size stipulated by Swedish legislation [
25]. The minimum requirement for a lying area in a lying hall is that it should be no less than 80% of the area of a single box which houses a horse of the same size, if the feeding area is placed outside the lying hall. The area requirement is calculated from the height of the withers, and does not consider the horse’s behaviors or need for individual space.
The highest number of horses was found during the night (1–4 AM) in all lying halls, indicating that horses will seek shelter during nighttime whatever the available lying area, as seen in another study [
27]. Since our studies were conducted during late autumn and early spring, there was a drop in temperature overnight, suggesting that the horses were seeking shelter due to weather conditions [
28,
29,
30,
32].
There was a wide range of time spent in the lying hall among the focal horses in Study 1, ranging from 6.6% to 35.2% of their time, during separate 24 h periods. This variation in use of lying halls is consistent with other studies and can vary due to weather or feed availability [
30]. The lying halls were all facing either southeast (Study 1) or southwest (Study 2), meaning that the radiation of the sun was similar. Lying hall 1 in Study 2 (
Figure 3) is less shaded by other buildings during afternoons compared to Lying hall 2 and some horses have been seen to stand there in on sunny days during the winter. The feeding stations restarted at 8 AM (Study 1) and 6 AM (Study 2) and this could explain the drop in horses each morning shortly before the restart. The same tendency for when lying periods occurred has been observed in other active open barns [
13], meaning that the routines of the housing system could have influenced the lying periods. In Study 1, consisting of 18 horses and 1 lying hall, the lying hall was never empty. This finding indicated that a larger herd divides into subgroups and visits the lying hall in turns, as Nilsson [
24] suggested.
In Study 2, the horses’ use of the lying hall increased from 14% to 33% when the available area increased. In comparing time spent in the two lying halls during period 3, we find that the horses preferred the larger lying hall (100 m
2) to the smaller one (80 m
2). This indicated that even a small increase in the lying area had an impact on the time spent in the lying hall. Although most of the horses spent all or nearly all of their time in the larger lying hall, some individuals preferred the smaller hall. In opting for the smaller hall, these horses had access to a greater lying area for themselves, instead of being squeezed in with the other horses in the lying hall next door. There could be several reasons for this choice. Some studies have found that a larger lying area leads to more frequent lying down [
21,
23]. Other studies have found that low-ranked horses are more frequently disturbed [
20], which might also have encouraged some horses to choose the less crowded larger lying hall. Individual spacing from other horses often depends on sex or age [
30,
33]. In Study 2, one horse was seen lying outside the lying hall during daytime when the horses had access only to the smallest available lying area (8 m
2). Consequently, we can speculate that this horse might have found it too crowded in the lying hall and required more individual space even though neither individual spacing nor rank was measured in this study.
In Study 2 we found that the horses demonstrated longer estimated sternal and lateral recumbency in the single boxes (10.5 m
2) and in the lying halls with a larger available lying area (18 m
2/horse), than they did in the lying halls with a smaller available lying area (8 m
2/horse). Still, the estimated average lying time in the single boxes was slightly lower (2 h and 40 min) than the length of 3 to 4 h reported in other studies [
4,
5,
12]. The lying time in single boxes was still longer than the 30 min to 2 h reported for feral horses [
8,
9,
10,
11], suggesting that the horses in single boxes obtained more lying time than horses in more natural circumstances. The horses also performed more standing rest when housed in the single boxes than in the lying halls. Since the lying halls were the only area in the open barns to be video recorded, it is possible that the horses performed resting behaviors outside the lying halls. Some horses could have performed standing rest outside when they only had access to the smaller lying area of 8 m
2/horse, due to competition for space. In addition, they would have had a better environmental overview outside the lying hall. Another factor that could have increased the lying time in the single boxes was that the bedding in the single boxes was shavings, which may have led to increased lying time as the horses were not inclined to forage from their straw bedding as they were in the lying halls.
Both the sternal and the lateral recumbency in the lying halls increased when the horses were offered 18 m
2 available lying area instead of 8 m
2 available lying area. This result is consistent with Fader & Sambraus [
21] and Raabymagle & Ladewig [
23], who also observed longer lying times in larger lying areas than in smaller ones. Fader & Sambraus [
21] found no correlation between number of lying halls and different lying times in their study of seven heterogeneous herds. This indicates that it is in fact the differences in available lying area which affect lying time, and not the separated lying areas when the lying area increased in Study 2 and could be due to the access to greater individual space afforded by larger lying areas. Nevertheless, estimated average lying times when the horses only had access to a lying area of 8 m
2/horse were no shorter than the lying times observed among feral horses [
8,
10,
11]. The five focal horses in Study 1 seemed to spend less time in lateral and sternal recumbency when comparing the time budgets between the two studies. This finding is difficult to analyze, since lying time has been found to differ between individual horses [
19]. Access to a comfortable and secure lying area might be a resource that horses compete for [
19,
20,
21]. Decreased lying time could be associated with inappropriate environmental conditions [
7], equating to a limited resource which could, in turn, impact their welfare. Total resting time, including sternal and lateral recumbency and standing rest, did not differ between different available lying areas in lying halls.
In both studies, the horses used the lying halls for purposes other than resting, such as standing attentive, which in Study 1 included foraging. Foraging was therefore separated from standing attentive in Study 2, where foraging from the straw bedding was shown to increase with increased lying area. Straw bedding in lying halls might decrease lying time when compared with other soft bedding due to disturbances caused by foraging [
27]. Such disturbances could explain the decrease in lying time in the smaller available lying areas. One advantage of straw bedding is that the horse-keeper can see if the horse has been lying down without video recording, and another is that straw has a positive environmental impact, if it is to be included in an ecological cycle. Offering straw outside the lying hall could be a solution to satisfy the horses’ eating requirements. In both the open barn systems, the horses were offered haylage from automatic, computer-controlled forage stations outside the lying halls, to meet the recommended requirement of 1.5 kg DM per 100 kg bodyweight. The forage feed intake rate is, on average, 22 min/kg DM [
34], which means that their estimated daily forage intake time is 3.5 h and suggests that straw is required to meet their need for long feeding times.
The data from this study are based on observations from two different active open barns with similar stable furnishings, such as lying halls with straw, gravel paddocks, and individual computer-controlled feeding stations. The layouts did differ, however, between the open barns, which may have influenced the lying times that were observed. Furthermore, geographical differences affecting daylight and climate may also have influenced the horses’ behavior, since the open barn used in Study 2 lies 600 km north of the open barn used in Study 1. The horses in both studies were all adult geldings and horses working on a medium level, which means that the horses in the two herds were comparable. Given the similarities between the barns and the horses, the results are equivalent and suggest that there is an optimal lying area per horse in the lying hall. However, it is also important to remember that this optimal lying area could differ in herds with mixed sexes, or herds comprising only mares, as they have different individual spacing needs [
34]. In this study, we had no evaluation of the ranks of the individual horses, which has also been reported to influence lying time [
20]. Using straw as the bedding material might have influenced the optimal lying area, since straw has been shown to decrease lying time, due to foraging [
27]. Another factor pertaining to bedding that could influence lying time is the horses’ prior experience with different bedding materials, which we had no record of.
The observations made through video recordings gave a good overview of the horses’ behaviors, and our results are based on quite a large sample. Although it can be difficult to see if time and treatment covariate, each horse in Study 2 acted as their own control, which lends credibility to our findings. Only five focal horses were used for the interval observations of Study 1, and although these were chosen randomly and were of representative age (10–16 years) and daily work levels, using another five horses may have affected the result due to individual differences. When using scan sampling, there is a possibility of missing some details, such as the duration between the logging of each observation and behaviors exhibited in those intervals. It is hoped, however, that these disadvantages are compensated for by the ability to analyze more animals in less time. In Study 2 there is missing data for one 24 h period in which the horses had access to a lying area of 18 m2/horse, due to a demolished fence between the lying hall and a second lying hall that was not in use. The statistics model used compensates for the missing data, meaning that the result is still valid.
The active barn system is suitable for urban horse-keeping and for riding schools with limited access to land for paddocks and grazing and meets all the horse’s basic needs. Overall, however, our observations suggest that the current minimum lying area requirements (at least those stipulated by Swedish legislation) might be too small for the domesticated horse, and that the minimum requirement could be increased in order to better safeguard their welfare. Our recommendation, in order to improve the welfare of horses kept in open barns, is to increase the minimum requirement of the lying area by a factor of 20–100%. This recommendation is based on the finding that to offer a lying area extended by only 20% (Lying hall 2 in Study 2) encouraged the horses to prefer that specific lying hall. Furthermore, increasing the available lying area increased both the use of the lying area and the lying time. Since it is crucial to the welfare of horses that they have the opportunity to get enough sleep, the choice of bedding is an important factor to consider. However, further studies are needed to ascertain the optimal lying area per horse and bedding material in a lying hall, in order to maximize the sleeping comfort of each individual.